1. Field of the Invention
The present invention relates to a device for cutting cylindrical tubes into tubes pieces. The cutting device of the present invention is particularly suitable for cutting predetermined lengths of tube pieces from a continuously formed spiral tube made from strips of cellulosic material, such as cardboard or paper, which has been provided with a coating of substance which forms a hard surface on at least a portion of the exterior of the tube.
2. Discussion of Background and Material Information
Cylindrical tubes may be formed from various materials such as cellulosic strips, and treated in different ways depending on their intended use. For example, cardboard tubes may be provided with a hard surface coating which is substantially uniform across their entire surface or only on a portion thereof as required by the situation.
It is conventional to form tubes in a continuous fashion on machines known as spiralers by helically winding a plurality of cellulosic strips, such as paper or cardboard, around a mandrel. The resultant cylinder in its rotation is continuously advanced in a longitudinal direction towards cutting and polishing stations located downstream from the forming station. As the continuously formed tube reaches the cutting station, conventional severing devices are brought into play to slice or cut individual units of desired size from the tube, which may be further subdivided into appropriate sized pieces as desired.
The apparatus used by the prior art to sever continuously formed tubes into pieces or to sever the said pieces, generally has at least one knife which cooperate with a special part of the mandrel supporting the tube or with a special mandrel so as to act against the tube to be cut witch is placed into rotation. In those instances where the cylinder to be cut is provided with a hard surface on at least a portion of its exterior during its formation, or after an initial cutting into tubular pieces, the cutting action of the knives of prior art apparatus often causes a disruption in the hard surface coating which may result in a peeling or scaling of the coating from the surface. It then becomes necessary to perform a subsequent finishing operation which may involve additional polishing in an attempt to repair the damaged surface.
The present invention is directed to a method and apparatus for cutting a coated cylinder into tubular pieces which minimizes peeling or scaling of the coated surface, and hence eliminates the necessity of an additional finishing operation. According to the present invention, an apparatus is provided whereby the coated surface of the tube is subjected to an operation which simultaneously grinds off the surface coating in a narrow band around the area of the tube to be cut while buffing the same so as to prevent feathering, rough edges, and the tendency of the coating to scale or peel. To this end, the apparatus of the present invention is equipped not only with at least one knife for cutting the tube and an apparatus to rotate the tube as it is being formed, but also with a unique arrangement including a grindstone or polishing wheel designed to move transversely towards and away from the tube to a controlled degree so as to precisely score a peripheral groove in the coated surface of the tube around the area where the tube is to but cut with a cutting knife being positioned to finish the cut beginning at the bottom of the furrow or groove formed by the polishing wheel. Although the grindstone or polishing wheel and the knife are programmed to act successively in the foregoing manner, the cutting action of the knife begins almost immediately upon removal of the surface coating and the scoring of the groove caused by the grindstone. The unique arrangement of elements of the apparatus of the present invention also permits the tube to be polished while it is being cut as well as immediately afterward to result with two pieces having smooth, cut end surfaces.
U.S. Pat. No. 3,711,996, BRADEN et al., discloses an apparatus which includes a mill wherein a plurality of rotating grinding wheels are passed by the peripheral surface of a mandrel on which a cylindrical cured cord reinforced rubber sleeve is supported in a direction perpendicular to the longitudinal axis of the mandrel so as to engage a sleeve to cut peripheral grooves in the sleeves while a plurality of rotating cutting blades pass the peripheral surface of the mandrel in a similar manner to sever the sleeve into a plurality of V-belts. Accordingly, the grinding wheels cause the initial openings of the V-shaped grooves through a substantial portion of the thickness of the sleeve while the knives, positioned in pairs, are designed to cut the straps by penetrating into the groove to sever through the relatively thin amount of rubber sleeve which remains. Thus, the goal of this prior art device is to first shape a groove in a relatively soft elastomeric material which is then severed into individual bands so as to result with belts which have been beveled to have a V-shaped configuration.
In contrast, the present invention is directed to solving a completely different problem of reducing or eliminating peeling or scaling of a relatively hard coating from a cylinder whose end surfaces after cutting into tubular pieces must be essentially planar and as perpendicular to the longitudinal axis of the tube as possible.